AJCC 8th Edition (2017) versus AJCC 7th Edition (2010) in thin melanoma staging

Area of Science:

• Dermatology
• Oncology
• Pathology

Background:

• The 8th Edition of the American Joint Committee on Cancer (AJCC) staging system for melanoma revised T1 categorization, removing mitotic count and adopting Breslow's depth sub-stratification.
• Despite advancements in early screening, thin melanoma continues to pose a significant mortality risk.
• Melanoma progression is understood to occur in two phases: radial growth phase (RGP) and vertical growth phase (VGP).

Purpose of the Study:

• To investigate the potential bio-histological factors influencing thin melanoma outcomes.
• To explore the correlation between melanoma growth phases and patient prognosis.
• To propose a refined understanding of thin melanoma subtypes based on growth characteristics.

Main Methods:

• Analysis of thin melanoma cases to identify distinct bio-histological subtypes.
• Classification of subtypes based on presence and extent of regression and micro-invasion.
• Correlation of identified subtypes with clinical outcomes and prognostic indicators.

Main Results:

• Thin melanoma can be categorized into three bio-histological subtypes: non-tumorigenic micro-invasive RGP, micro-invasive RGP with regression, and micro-invasive tumorigenic VGP.
• Extensive regression (>75%) in micro-invasive RGP may indicate the presence of a VGP clone with uncertain tumorigenic potential.
• The study suggests a link between the specific growth phase (RGP vs. VGP) within thin melanomas and their overall prognosis.

Conclusions:

• The prognosis of thin melanoma is likely influenced by its underlying bio-histological subtype and growth phase.
• Re-evaluation of melanoma staging may benefit from incorporating growth phase characteristics beyond Breslow's depth.
• Further research into the biological behavior of thin melanoma subtypes is warranted to improve patient outcomes.